(a) Field of the Invention
The present invention relates to a fuel cell stack. More particularly, the present invention relates to an engaging structure of a fuel cell stack.
(b) Description of the Related Art
A fuel cell system is a kind of electric generation system that generates electrical energy through an electrochemical reaction between a fuel (typically hydrogen) and oxygen. Fuel cell systems have begun to be applied to vehicles in an effort to reduce the reliance on internal combustion engines.
As such these types of fuel cell systems include a fuel cell stack, a fuel (e.g., hydrogen) supply unit that supplies hydrogen to the fuel cell stack, an oxidant (e.g., air) supply unit that supplies air to the fuel cell stack, and a heat/water management device that removes water and reaction heat from the fuel cell stack and that controls an operational temperature of the fuel cell stack.
The fuel cell stack is formed in an electricity generator set in which tens to hundreds of unit cells are continuously arranged. In particular, a unit cell is formed by disposing separators on both sides with a membrane-electrode assembly (MEA) interposed therebetween. In the separator, a flow channel that supplies fuel, e.g., hydrogen, and an oxidant, e.g., air, to the MEA and that circulates a coolant therethrough is formed, and a gasket for sealing the fluid therein is interposed between the separator and the MEA.
Such a fuel cell stack also includes an end plate that is installed at the outermost ends (both sides) of continuously stacked unit cells, and the end plate is engaged through an engaging device so that when installed the end plate presses unit cells together. Here, a surface pressure between unit cells from the engaging device is directly related to material transfer resistance within a gas diffusion layer and ohmic loss by increase of contact resistance and thus it is essential to appropriately maintain an engaging force of unit cells to obtain a good stack performance.
However, because a fuel cell stack that is mounted at a vehicle requests a high performance, a plurality of unit cells of about 1V are stacked together (e.g., 100-300 or more) and thus the entire stack length is increased. Accordingly, a mechanical structure of the fuel cell stack becomes unstable and the fuel cell stack may have a weakened structure.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.